I prefer hardcover over paperback for exactly the same reasons as Sakura_Weller. I quite like the weight.
That said, I HATE taking hardcovers on the road and whereas damaging a hardback feels like a cardinal sin, a paperback doesn't seem to feel so bad when it gets a bit dog-eared.
As for digital, I don't own an e-reader and refuse to read more than ~12 pages on my monitor. I'm a traditionalist for books...paper please!

In general, I buy paperbacks. It saves space--I have thousands of books--and is cheaper. When I decide a book is a favorite, then I'll upgrade to a hardcover. This ensures the book stays in the best condition possible.

I will read either hardcover or paperback but I prefer paperback since they are easier to turn pages in. As for digital reading I would like to get started with it as I continue to realize that moving my books from point A to point B is becoming more and more of a hassle as my collection increases. Of course having a book in your hands is more satisfying in my personal opinion however I wouldn't mind switchign to a nook or kindle.

Either paper or hardback is good for me but i definitely don't like reading on a screen. The convenience of carrying around 300 books, movies and whatnot where ever i go just doesn't appeal to me. Needing a lamp to read by is not a concern for me and I never have to think about battery life with a real book. Plus they don't feel right compared to a real book because I'm so attached to the sensory experience of a book. When i curl up with a book i want to feel the paper in my hands and hear the pages rustle.

Paperback. I don't collect books so I don't care about getting the highest quality version. Paperbacks are cheaper and easier to carry around, although portability is less of a concern now that I drive everywhere rather than use mass transit.